Conventionally, these kinds of low-pressure dome type refrigerant compressors include a compression element arranged in an upper position and a motor arranged in a lower position inside its casing that has an oil reservoir at its lower portion, and a suction pipe is opened inside the casing. In regard to a passage structure of gas refrigerant inhaled from the suction pipe, there are the types (A), (B) and (C) as follows.
(A) A suction pipe is opened oppositely to an outer surface of a lower portion of a stator of a motor inside a casing, and inhaled gas is guided from a gap around the periphery of the stator to a compression element side arranged in an upper position (refer to Japanese Utility Model Laid-Open Publication No. SHO 62-110593).
(B) A suction pipe is opened to a space above a motor inside a casing, and inhaled gas is guided to a compression element side by way of a short passage (refer to Japanese Patent Laid-Open Publication No. HEI 2-125986).
(C) A lower portion of a motor is covered with a cover, and a suction pipe is opened inside the cover, so that inhaled gas is guided to a compression element side through an air gap of the motor (refer to Japanese Patent Laid-Open Publication No. SHO 63-90695).
However, in the structure of the above (A), the inhaled gas is made to pass only through the peripheral portion of the motor, this causes a problem that an insufficient motor cooling effect results. Furthermore, when liquid refrigerant is inhaled together with inhaled gas, the liquid refrigerant passes through the peripheral portion of the stator to directly fall to an oil reservoir, and this causes a problem that it dilutes the oil and reduces the oil concentration to incur deficient lubrication.
In the structure of the above (B), there is almost no loss of pressure of the inhaled gas, however, cooling of the motor is insufficient. Thus, similar to the structure of (A), deficient lubrication by the liquid refrigerant occurs.
In the structure of the above (C), the motor cooling effect is satisfactory because the inhaled gas is made to pass through the air gap; however, suction pressure loss occurs. Furthermore, the liquid refrigerant can be reserved inside the cover, however, since its capacity is small, it cannot cope with, in particular, a liquid reflux of a multi-system having a plurality of indoor units or the like. Furthermore, once reserved liquid can be hardly discharged, and this may problematically cause an inoperable state of the apparatus.
Accordingly, it is an object of the present invention to provide a refrigerant compressor capable of satisfactorily ensuring a motor cooling effect, reducing suction pressure loss and preventing the possible occurrence of dilution of oil in the stage of liquid reflux, thereby allowing an improved lubricating performance to be achieved.